A trigger switch is a switch designed for an electric tool such as an electric saw blade, and is called a trigger switch because the shape of its operation unit resembles a trigger. A speed-controllable trigger switch capable of continuously controlling a motor rotational speed has also been developed as the trigger switch. This can, for example, increase and decrease the rotational speed of the electric saw blade.
For example, as illustrated in FIG. 7, there is known a trigger switch as a speed-controllable trigger switch 100 as described above in which a sliding contact 103 is slid to a variable resistor 102 provided on a control circuit board 101 to control the motor speed by resistance change.
However, in the speed-controllable trigger switch 100 having adopted the sliding contact 103, conduction defects due to mechanical abrasion, mechanical wear, and vibration occur in the sliding contact 103 and the variable resistor 102, to shorten mechanical lives of the sliding contact 103 and the variable resistor 102 and make the output unstable.
In order to solve this problem, an electric tool trigger switch disclosed in Patent Document 1 has been proposed.
As illustrated in FIG. 8, an electric tool trigger switch 200 disclosed in Patent Document 1 includes a sliding operation unit 210 incorporated in a case 201 and moving in conjunction with the retracting operation of the trigger lever 202. The sliding operation unit 210 includes a permanent magnet 212 attached to the side surface of a speed controller 211 and a circuit board 220 provided with a magnetic field sensor 221 at a position facing the permanent magnet 212.
In the electric tool trigger switch 200, the speed controller 211 moves in a retracting direction in conjunction with a retracting operation of a trigger lever 202. At this time, a signal is generated by a change in magnetic field received by the magnetic field sensor 221, and a motor speed is controlled based on the generated signal.